Biomedical subjects

Xiang Ji

Publications and source records attributed to Xiang Ji.

22 records · Page 2Linked to original sources

PubMed2003

[Ontogenetic shifts in sexual dimorphism in head size and food habits of Eremias brenchleyi].

Studies on the ontogenetic shifts in sexual dimorphism in head size (head length and width) and food habits of Eremias brenchleyi were studied. The results showed that adult E. brenchleyi had no obvious sexual dimorphism in body size (SVL). Both sexes differed in head size since hatching, with males having larger heads than females. This sexual dimorphism was much more pronounced between adults than between juveniles (including hatchlings), largely because the increase velocity of head size of males with SVL was faster than that of females. Hatchlings had relatively larger heads to SVL than juveniles and adults, presumably because E. brenchleyi embryos allocated relatively more resources for early survival and growth of hatchlings. Head size of both sexes overall showed an allometric growth pattern with SVL increase ontogeny. Lizards of different sizes and sexes differed, in certain degrees, in food niche breadth and niche overlap. However, no direct evidence showed a noticeable contribution of the divergence in head size to the segregation of food niche between males and females, thereby mitigating the competition between both sexes.

Animals↗

PubMed2002

Influence of incubation temperature on hatching success, energy expenditure for embryonic development, and size and morphology of hatchlings in the oriental garden lizard, Calotes versicolor (Agamidae).

We incubated eggs of Calotes versicolor at four constant temperatures ranging from 24 degrees C to 33 degrees C to assess the effects of incubation temperature on hatching success, embryonic use of energy, and hatchling phenotypes that are likely to affect fitness. All viable eggs increased in mass throughout incubation due to absorption of water, and mass gain during incubation was dependent on initial egg mass and incubation temperature. The average duration of incubation at 24 degrees C, 27 degrees C, 30 degrees C, and 33 degrees C was 82.1 days, 60.5 days, 51.4 days, and 50.3 days, respectively. Incubation temperature affected hatching success, energy expenditure for embryonic development, and several hatchling traits examined, but it did not affect the sex ratio of hatchlings. Hatching success was lowest (3.4%) at 33 degrees C, but a higher incidence of deformed embryos was recorded from eggs incubated at this temperature compared to eggs incubated at lower temperatures. Most of the deformed embryos died at the last stage of incubation. Energy expenditure for embryonic development was, however, higher in eggs incubated at 33 degrees C than those similarly incubated at lower temperatures. A prolonged exposure of eggs of C. versicolor at 33 degrees C appears to have an adverse and presumably lethal effect on embryonic development. Hatching success at 24 degrees C was also low (43.3%), but hatchlings incubated at 24 degrees C did not differ in any of the examined traits from those incubated at two intermediate temperatures (27 degrees C and 30 degrees C). Hatchlings incubated at 33 degrees C were smaller (snout-vent length, SVL) than those incubated at lower incubation temperatures and had larger mass residuals (from the regression on SVL) as well as shorter head length, hindlimb length, tympanum diameter, and eye diameter relative to SVL. Hatchlings from 33 degrees C had significantly lower scores on the first axis of a principal component analysis representing mainly SVL-free head size (length and width) and fore- and hindlimb lengths, but they had significantly higher scores on the second axis mainly representing SVL-free wet body mass. Variation in the level of fluctuating asymmetry in eye diameter associated with incubation temperatures was quite high, and it was clearly consistent with the prediction that environmental stress associated with the highest incubation temperatures might produce the highest level of asymmetry. Newly emerged hatchlings exhibited sexual dimorphism in head width, with male hatchlings having larger head width than females.

Animals↗

PubMed2002

[Geographic variation in female reproductive characteristics and egg incubation of Eumeces chinensis].

Geographic variation in female reproductive characteristics and egg incubation of Chinese skink (Eumeces chinensis) was studied by using two populations from eastern (Lishui, Zhejiang) and southern (Shaoguan, Guangdong) China, respectively. The results showed that female adults of the two populations both laid a single clutch per breeding season, and the clutch size, clutch mass, and egg mass had a positive correlation with female SVL. There was obvious geographic variation in head shape of females, reproductive characteristics, timing date of oviposition, and thermal dependence of egg incubation between two populations. Skinks from Shaoguan began to lay eggs in mid-May, approximately two weeks earlier than the timing date of skinks from Lishui. Skinks from Shaoguan produced more but smaller eggs. The size-specific (SVL) clutch size of skinks from Shaoguan outnumbered that of skinks from Lishui by 2.8 eggs. It implied there was a trade-off between the number and the size of offspring between populations, because there was no difference in size-specific clutch mass among skinks from both populations, and skinks within a population could produce larger clutches without a concomitant reduction in egg mass. Overall, compared to eggs incubated under 32 degrees C, eggs incubated under 24 degrees C could produce larger (SVL) and well-developed hatchlings with less unutilized yolks. Compared to eggs from Lishui incubated under the same temperature of 24 degrees C and 32 degrees C, eggs from Shaoguan produced hatchlings with smaller body wet mass and carcass dry mass. Accordingly, there was geographic variation in suitable range of incubation temperatures, and eggs laid by skinks from Lishui could successfully incubate in a wider range of temperatures.

Animals↗

PubMed2002

[Thermal tolerance, diel variation of body temperature, and thermal dependence of locomotor performance of hatchling soft-shelled turtles, Trionyx sinensis].

The thermal tolerance, body temperature, and influence of temperature on locomotor performance of hatchling soft-shelled turtles (Trionyx sinensis) were studied under dry and wet conditions, and the selected body temperature of hatchlings was 28.0 and 30.3 degrees C, respectively. Under wet condition, the critical thermal maximum and minimum averaged 40.9 and 7.8 degrees C, respectively. In the environments without thermal gradients, the diel variation of body temperature was highly consistent with the variation of both air and water temperatures, and the body temperature was more directly affected by water temperature than by air temperature, which implied that the physiological thermoregulation of hatchling T. sinensis was very weak. In the environments with thermal gradients, hatchling turtles could maintain relatively high and constant body temperatures, primarily through behavioral thermoregulation. The locomotor performance of hatchling turtles was highly dependent on their body temperature. Within a certain range, the locomotor performance increased with increasing body temperature. In our study, the optimal body temperature for locomotor performance was 31.5 degrees C, under which, the maximum continuous running distance, running distance per minute, and number of stops per minute averaged 1.87 m, 4.92 m.min-1, and 6.2 times.min-1, respectively. The correspondent values at 33.0 degrees C averaged 1.30 m, 4.28 m.min-1, and 7.7 times.min-1, respectively, which indicated that the locomotor performance of hatchling turtles was impaired at 33.0 degrees C. Therefore, extremely high body temperatures might have an adverse effect on locomotor performance of hatchling turtles.

Animals↗